Merge pull request #1848 in SNORT/snort3 from ~BBANTWAL/snort3:fix_offload_sclear...

Merge pull request #1848 in SNORT/snort3 from ~BBANTWAL/snort3:fix_offload_sclear to master

Squashed commit of the following:

commit 2a913fe450cc4d25ed02fed62827c97c98b83791
Author: Bhagya Tholpady <bbantwal@cisco.com>
Date:   Tue Nov 19 14:35:19 2019 -0500

    detection: disable rule evaluation when detection is disabled for offload packets

commit 520f55a8bfea4f6b43b5a452e9beaad6dfa837c0
Author: Bhagya Tholpady <bbantwal@cisco.com>
Date:   Tue Nov 19 12:53:21 2019 -0500

    flow: check if there are offloaded packets in the flow before clearing out the alert count

commit 12163b08cc3718f82b1df982dee826aff31ec7b8
Author: Bhagya Tholpady <bbantwal@cisco.com>
Date:   Mon Nov 18 14:26:24 2019 -0500

    detection: move the inspector manager thread local flag used to determine whether or not to call inspector clear to context